This invention relates to a pressure-resistant tank having a casing composed of part-cylindrical casing portions with parallel longitudinal axes fitted between hollow longitudinal members, wherein opposite longitudinal members are interconnected by tie rods extending vertically through the tank interior.
U.S. Pat. No. 4,840,282 discloses a pressure-resistant tank of this type, which is configured as a tank container. There, the tank casing has a substantially clover-leaf shaped cross-section formed by four part-cylindrical casing portions which are fitted between four tubular longitudinal members.
Based on the current ISO container standards, the known configuration results in a circumferential length of the individual casing portions which does not exceed the maximum possible rolling width of about 2 m. Welds are therefore necessary only between the casing portions and the tubular longitudinal members while they are not required within the casing portions themselves.
However, the specified rolling width of about 2 m can only be achieved by "surface cold rolling" of an initially hot-rolled sheet material. With the rolling technique presently available in Europe, cold-rolled coils produced continuously from wide strip material can be obtained up to a width of about 1.6 m. If it is attempted to build dual-shell tanks in accordance with the principle known from U.S. Pat. No. 4,840,282 it will be apparent that the two casing portions require circumferential dimensions which are substantially in excess of the above-specified rolling width, if the ISO framework profile is to be fully utilized.
By longitudinally joining two cold-rolled sheets each having a width of about 1.6 m, a dimension in the circumferential direction of at most about 3.2 m can be obtained for a casing portion provided with one weld. In view of the desired utilization, of the ISO profile this dimension is still insufficient for building a dual-shell tank.